Section 1 Electrical Installations

1.1.1  For the hull structure and associated liquefied gas cargo containment system, hazardous areas are to be determined, and electrical equipment is to be selected, in accordance with IEC 60092: Electrical installations in ships – Part 502: Tankers - Special features.

For topsides process facilities, the hazardous areas and electrical equipment selected for these areas should be established from suitable recognised hazardous area guidance, i.e. NFPA 497 Recommended Practice for the Classification of Flammable Liquids, Gases, or Vapors and of Hazardous (Classified) Locations for Electrical Installations in Chemical Process Areas or EI IP-MCSP-P15 Model Code of Safe Practice Part 15 Area Classification Code for installations handling flammable fluids. However, whichever Standard is selected for the classification of topsides process hazards, it should be ensured that it gives a suitably conservative determination of the defined hazardous area. Reference should also be made to the requirements stipulated within Pt 7, Ch 2 Hazardous Areas and Ventilation.

1.1.2 Electrical installations shall be such as to minimise the risk of fire and explosion from flammable products.

1.1.3 Electrical installations shall be in accordance with Pt 6, Ch 2 Electrical Engineering and Pt 7, Ch 2 Hazardous Areas and Ventilation where installations are located in hazardous areas. Reference is made to the recommendation published by the International Electrotechnical Commission, in particular to publication IEC 60092-502:1999 Electrical installations in ships - Part 502: Tankers - Special features.

1.1.4 Electrical equipment or wiring should not be installed in hazardous areas unless essential for operational purposes or safety enhancement.

1.1.5 Where electrical equipment is installed in hazardous areas as provided in Pt 11, Ch 10, 1.1 General requirements 1.1.4 it shall be selected, installed and maintained in accordance with Standards not inferior to IEC 60092-502:1999 (see Clause 6, Clause 7 and Clause 9) Electrical installations in ships - Part 502: Tankers - Special features. Equipment for hazardous areas shall be evaluated and certified or listed by an accredited testing authority or notified body recognised by the Administration. Automatic isolation of non certified equipment on detection of a flammable gas shall not be accepted as an alternative to the use of certified equipment.

1.1.6 To facilitate the selection of appropriate electrical apparatus and the design of suitable electrical installations, hazardous areas are divided into zones in accordance with recognised Standards such as Pt 7, Ch 2, 1 Hazardous areas – General and Pt 7, Ch 2, 2 Classification of hazardous areas or publication IEC 60092-502 Electrical installations in ships - Part 502: Tankers – Special features.

1.1.7 Electrical generation and distribution systems, and associated control systems, shall be designed such that a single fault will not result in the loss of ability to maintain cargo tank pressures, as required by Pt 11, Ch 7, 1.8 Availability 1.8.1 (a), and hull structure temperature, as required by Pt 11, Ch 4, 5.1 Materials 5.1.2, within normal operating limits. Failure modes and effects shall be analysed and documented to a standard not inferior to IEC 60812 Analysis techniques for system reliability Procedure for failure mode and effects analysis (FMEA).

1.1.9 Electrical depth sounding or log devices and impressed current cathodic protection system anodes or electrodes shall be housed in gastight enclosures.

1.1.10 Submerged cargo pump motors and their supply cables may be fitted in cargo containment systems. Arrangements shall be made to automatically shut down the motors in the event of low liquid level. This may be accomplished by sensing low pump discharge pressure, low motor current, or low liquid level. This shutdown shall be alarmed at the cargo control station. Cargo pump motors shall be capable of being isolated from their electrical supply during gas-freeing operations.

1.1.11  Electrical equipment that is located in either enclosed or open non hazardous areas and is to remain operational during catastrophic emergency conditions (i.e. major hydrocarbon release scenarios) is to be certified for operation in Zone 1 hazardous areas. However if such emergency equipment is not certified for operation in Zone 1 hazardous areas, the continued operation of this equipment maybe acceptable if it is demonstrated that the equipment is appropriately protected against potentially coming into contact with a flammable atmosphere by being located in an enclosed non-hazardous area, with appropriate mitigating measures (i.e. enclosed non-hazardous area is equipped with gas tight barriers, gas tight doors, rated gas dampers, suitable gas detection within the enclosure and its ventilation air intakes, etc.). See Pt 7, Ch 2, 8.1 General 8.1.6.

1.2.1  Hazardous area is an area in which an explosive gas atmosphere is or may be expected to be present, in quantities such as to require special precautions for the construction, installation and use of electrical apparatus.

1. Zone 0 hazardous area is an area in which an explosive gas atmosphere is present continuously or is present for long periods.
2. Zone 1 hazardous area is an area in which an explosive gas atmosphere is likely to occur in normal operation.
3. Zone 2 hazardous area is an area in which an explosive gas atmosphere is not likely to occur in normal operation and, if it does occur, is likely to do so infrequently and for a short period only.

1.2.2  Non-hazardous area is an area in which an explosive gas atmosphere is not expected to be present in quantities such as to require special precautions for the construction, installation and use of electrical apparatus.

1.2.3  See also Pt 7, Ch 2, 1.2 Definitions and categories.